US780504A - Controller for alternating-current motors. - Google Patents

Description

PATENTED JAN. 24, 1905.

R. P. JACKSON.

CONTROLLER FOR ALTERNATING CURRENT MOTORS.

APPLIOATION FILED JUNE 6v 1904.

717 EylINVENTOR WITNESSES:

QM) 6. 5M

UNITED STATES Patented January 24, 1905,:

PATENT OEEIcE.

RAY P. JACKSON, OF VVILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A COR- PORATION OF PENNSYLVANIA.

CONTROLLER FOR ALTERNATlNG-CURRENT MOTORS.

SPECIFICATION forming part of Letters Patent No. 780,504, dated January 24, 1905.

Application filed June 6, 1904. Serial No. 211,371.

To all whom it puny concern:

Be it known that I, RAY P. JACKSON, a citizen of the United States, and a resident of I/Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Controllers for Alternating-Current Motors, of which the following is a specification.

My invention relates to controllers for electric motors which are operated by means of alternating-current energy; and it has for its object to provide means for reducing and preventing arcing between the circuit making and breaking contact surfaces and consequent injuries thereto.

The speeds of alternating-current motors may be varied by varying the voltages applied to them, and this is commonly done by varying the active lengths of the windings of transformers which supply energy to the motors. In the operation of controllers which are employed for varying the active lengths of such transformer-windings the motor-circuits are broken at each step in the voltage or portions of the main transformer-winding are temporarily short circuited, and danger ous and destructive arcs are usually produced when either of these changes takes place. Another difficulty which has been experienced in the construction of controllers for the purpose described has been due to the fact that in passing from higher voltage steps to lower voltage steps the arcing may be very serious, While that occurring when passing from lower voltage steps to higher voltage steps may be of comparatively little consequence.

My invention provides means for controlling motors in substantial accordance with the method described, but which avoids dangerous and destructive arcing between the parts of the controller which make and break contact with each other regardless of whether the controller is operated to supply increasing or'decreasing voltages to the translating devices and is illustrated in the single figure of the accompanying drawing.

Single-phase alternating-current energy is Supplied from a suitable source 1 to a main auto-transformer winding 2, which is suitably subdivided by means of leads 3 4i 5 6, 850., respectively provided with contact-lingers 7 8 9 10, &c., and to one terminalof which an alternating-current motor 11 or other suitable translating device or devices is connected, the other terminal or terminals of the motor being connected to contact-linger 12. If desired, a two-winding transformer may be employed instead of the auto'transformer winding, the secondary winding of which is suitably subdivided in a manner similar to that here shown for the auto-transformer. An auxiliary transformer 18, having two primary windings designated, respectively, as 14 and 15, and a secondary winding 16 is connected to the various circuits in a manner to be hereinafter more fully set forth for the purpose of reducing and preventing arcing between the contact-fingers and drum-segments. One terminal of the primary winding 14: is connected to contact-finger 17, which is adapted to engage with drum-segment 18, and the other terminal is connected to contact-finger 12. One terminal of the primary winding is connected to the source 1 and its other terminal is connected to contact-tinger19, which is adapted to be electrically connected temporarily and at proper instants to contacttinger 20 by means of conducting-strips 21 21 21 &c., mounted upon the drum 22. In a similar manner conducting-strips 23 2323", &c., are adapted to engage with and connectcontact-fingers 24 and 25, which are respectively connected to the terminals of the secondary winding 16.

A circuit is established through the motor 11 by the engagement of drum-segments 26 and 27 with contact-fingers 7 and 12 when the controller-drum 22 is moved to position a, and a voltage is impressed upon the motor 11 that is equal to the difference of potential existing between terminal 28 of the transformer-winding 2 and the point in that winding with which the terminal 3 is connected. In moving to position Z) of the controller-drum 22 drum-segment 29 engages contact-linger 8, and conducting-strip 21 simultaneously connects lingers 19 and 20, and immediately thereafter drumsegment 18 engages contact-finger 17 The portion of the main transformer-winding 2 included between the leads 3 and i is then shortcircuited through the primary winding 14 of the auxiliary transformer 13; but at the same time the other primary winding is energized from the source 1, and the potentials of the contact-fingers 7 and 8 are made approximately equal. Then when drum-segment 27 is disengaged from contact-finger '7 very little arcing occurs between the said parts. As soon as this latter operation occurs the conducting-strip 21 is disengaged from contactlingers 19 and 20, and the voltage applied to themotor-11 is only opposed by the impedance of the coil 14:, and this is removed from the circuit when the controller-drum 22 has been moved to the full position Z), very little or no arcing occurring when the contact-finger 8 passes from the drum-segment 29 to the drumsegment 30, since the potentials of the drumsegments 28 and 29 are substantially equal. If it is desired to impress a lower voltage upon the terminals of the motor 11 when the controller-drum 22 is in position 0, it is necessary to return to the position I), and in doing so the conducting-strip 23 engages contact-fingers 24 and 25, so that when drum-segment 31 is disengaged from contact-finger 9 and drum-segment 32 engages therewith the secondary winding 16 of the auxiliary transformer 13 opposes the flux produced by the winding 14:,and consequently very little sparking occurs in this part of the operation. When drum-segment next engages with contact-finger 8 and later when drum-segment 32 is disengaged from contact-finger 9, very little arcing occurs, since drum-segments 30 and 32 are of approximately equal potential. I desire it to be understood that the single motor shown and described is indicative of either one or a plurality of any suitable translating devices and that such translating devices when more than one are employed may be connected in either series or parallel relation.

I claim as my invention 1. The combination with a source of alternating current energy, a subdivided main transformer winding connected thereto, a translating device having a terminal connected to said winding and means for connecting the other terminal to the successive points of subdivision of the main winding, of an auxiliary trans former comprising three windings,means for connecting the first of these windings between successive points of subdivision of the main winding, means for temporarily connecting the second auxiliary transformerwinding to the source of energy, and means for temporarily short-circuiting the third auxiliary transformer-winding.

2. The combination with a source of vari able voltage alternating current energy. a translating device having a terminal connected directly thereto, and means for connecting the other terminal to points connected with said source but differing progressively in voltage, of an auxiliary transformer comprising three windings, means for connecting the lirst of these windings between the points diifering progressively in voltage, means for temporarily connecting the second auxiliary winding to said source and means for temporarily short-circuiting the third auxiliary Winding.

In testimony whereof I. have hereunto subscribed my name this 27th day of May, 190

RAY I. JACKSON. l/Vitnesses:

H. B. MYER, BIRNEY HINEs:

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